The invention is in the field of nucleic acid sequences capable of regulating transcription, particularly sequences that may promote transcription during embryogenesis in plants.
Most of the information about seed-specific gene expression comes from studies of genes encoding seed storage proteins like napin, a major protein in the seeds of Brassica napus, or conglycinin of soybean. Upstream DNA sequences directing strong embryo-specific expression of these storage proteins have been used successfully in transgenic plants to manipulate seed lipid composition and accumulation (Voelker et al., 1996). However, expression of storage protein genes begins fairly late in embryogenesis. Thus, promoters of seed storage protein genes may not be ideal for all seed-specific applications. For example, storage oil accumulation commences significantly before the highest level of expression of either napin (Stalberg et al., 1996) or conglycinin (Chen et al., 1988) is achieved. It is, therefore of interest to identify other promoters which may modulate expression of genes in developing plant embryos.
A variety of transcriptional regulatory regions that may be active during plant embryogenesis are known, as disclosed for example in: U.S. Pat. No. 5,792,922 issued Aug. 11, 1998 to Moloney; U.S. Pat. No. 5,623,067 issued Apr. 22, 1997 to Vandkerckhove et al.; International Patent Publication WO9845461 published Oct. 15, 1998. There remains a need for alternative transcriptional regulatory regions.
FATTY ACID ELONGATION1 (FAE1) genes encode condensing enzymes involved in plant very long chain fatty acid biosynthesis. The FAE1 condensing enzyme is thought to be localized in the endoplasmic reticulum where it catalyzes the sequential elongation of C18 fatty acyl chains to C22 in length (Kunst et al., 1992). FAE1 genes have been cloned and described recently by James et al. (1995), International Patent Publication WO 96/13582.
In one aspect, the invention provides transcriptional regulatory regions derived from FAE1 genes. The transcriptional regulatory regions of the invention may be useful in promoting early seed-specific transcription of heterologous sequences to which they are operably linked. The transcriptional regulatory regions of the invention may be used in a wide variety of plants, including Brassica sp., Arabidopsis and other plant species. DNA constructs comprising the transcriptional regulatory sequences of the invention may be active during fatty acid or lipid biosynthesis in the plant embryo. Certain embodiments of the constructs of the invention may be used in transgenic plants to promote expression of heterologous sequences in developing seeds. In various embodiments, the constructs of the invention may be used to mediate gene expression that affects seed lipid metabolism, or seed protein composition or seed carbohydrate composition, or seed development. In alternative embodiments, the transcriptional regulatory regions of the invention may also be useful for the production of modified seeds containing novel recombinant proteins which have pharmaceutical, industrial or nutritional value.